Low mass balanced latch mechanism having resilient manual operating lever



Apnl 9, 1968 H. L. PEEK ET AL 3,377,575

LOW MASS BLANCED LATCH MECHANISM HAVING RESILIENT MANUAL OPERATING LEVER Filed Deo.

United States Patent O 3,377,575 LOW MASS BALANCED LATCH MECHANISM HAVING RESILIENT MANUAL OPERATING LEVER Henry L. Peek, Wellesley, and George K. Beuham, Somerville, Mass., assiguors to Allis-Chalmers Manufacturing Company, Milwaukee, Wis. Filed Dec. 22, 1965, Ser. No. 515,575 7 Claims. (Cl. 335-167) ABSTRACT OF THE DISCLOSURE A hydraulic pilot valve which is biased closed is momentarily opened by unlatching of a pivotable reset lever arm. The reset arm is latched by a pivotable low mass lbalanced latch `which is biased to a latched position against a stop. The latch is permitted to rotate to unlatched position wherein it releases the reset arm either by manual means or by a solenoid. These manual means take the form of a lever having a resilient portion for engaging and releasing the latch which is adapted to bend out of the.way when the latch snaps back to latched position.

This invention relates generally to latch mechanisms which are used to perform useful functions and which can be tripped either automatically or manually.

The present invention is embodied in a latch mechanism used to control (open and close) a pilot valve in the hydraulic control system which operates an electric circuit breaker. For example, in a hydraulic system of the foregoing type, the pilot valve is normally maintained in one condition by a latch mechanism to keep the circuit |breaker from closing. Tripping of the latch mechanism causes the pilot valve to assume another condition wherein it causes the circuit breaker to close. It is necessary in some cases, however, that the latch mechanism be reset immediately to reclose the pilot valve and prevent dumping of oil fro-m the hydraulic system. Resetting of the latch mechanism can be and usually is accomplished in response to movement of some component such as a ram in the hydraulic system or the circuit breaker.

Heretofore, latch mechanisms of this type were susceptible to shock and vibration which caused accidental tripping of the latch mechanism or sometimes prevented proper resetting of the latch mechanism. This susceptibility to shock and vibration resulted from such factors as imbalance of masses in the latch mechanism components, off-center points of rotation, location of masses at the end of long lever arms or cantilevers, overly critical tolerances, force moments in several planes and the like. In addition, since such latch mechanisms could be tripped manually as Iwell as automatically, there was danger to the person tripping the latch mechanism manually, if his hand were still on or near the manual operating lever and the latch mechanism reset and retripped automatically thereby causing movement of the lever.

Therefore, it is an object of this invention to provide an improved latch mechanism which overcomes the aforesaid drawbacks, which is reliable in use, and which is relatively economical to manufacture.

Another object is to provide a latch mechanism having a latch which is perfectly balanced about its center of rotation to reduce its susceptibility to shock.

Another object is to provide a latch mechanism having low mass components located and operative in optimum locations with respect to each other and their supporting frame so as to reduce reaction to shock.

Another object is to provide a latch mechanism hav- 3,377,575 Patented Apr. 9, 1968 ing improved manual tripping means which permit trip free operation.

Another object is to provide improved tripping means which comprise a low mass resilient operating lever which is safe for a human operator to use.

Other objects of the invention will hereinafter appear.

The accompanying drawing illustrates a preferred embodiment of the invention but it is to be understood that the embodiment illustrated is susceptible of modifications with respect to details thereof without departing from the scope of the appended claims.

In the drawing:

FIG. 1 is a side elevational view, partly in section, of a latch mechanism embodying the present invention and shows the latch mechanism in latched condition;

FIG. 2 is a top plan view of the latch mechanism shown in FIG. 1;

FIG. 3 is a view of the latch line III-III of FIG. l; and

FIG. 4 is a view of the manual operator of the latch mechanism taken along line IV-IV of FIG. 2.

Referring to FIG. 1 of the drawing, the numeral 10 designates a latch mechanism embodying the present invention. Latch mechanism 1t) is shown associated with a pilot valve device 12 upon which it performs a useful function. For example, device 12 comprises a plunger 14 which has a iirst position (shown), which is movable to a second position (upward) after unlatching of latch mechanism 10 and which is movable back to its rst position by a spring 15 after resetting of latch mechanism 10. As will be understood, latch mechanism 10 could be employed with devices other than pilot valve device 12.

Pilot valve device 12, .in addition to effecting operation of a hydraulic system, also effects upward movement of a ram 36 to reset latch mechanism 10` after the latter has tripped and plunger 14 has moved upward.

Latch mechanism 10 comprises a support or bracket 16 upon which its component parts are mounted and which adapts it for mounting in association with pilot valve device 12, ram 36 or other devices.

A movable member such as a reset arm 18 is pivotably mounted on a pivot pin 20l which is supported on support 16. Pivot pin 20 is located at a pivot point close to the center of reset arm 18 so that the reset arm is nearly balanced. Reset arm 18 has a iirst or latched position (shown) wherein it is maintained by a latch 22 and is movable counterclockwise to a second or unlatched position to etfectmovement of plunger 14 of pilot valve device 12. Counterclockwise movement of reset arm 18 is effected by biasing means such as a pair of springs 24 and 24a which are located in a pair of tubes 26 and 26a. respectively, which are :mounted on studs 28 and 28a, respectively, which depend from pilot valve device 12. The springs 24 and 24a bear against a plate 30 which in turn bears" against reset arm 18 and are held under compression when the reset arm is latched in its rst position.

Reset arm 18 is provided at one end with a latch roll 32 which is rotatable on a latch roll pivot pin 34 mounted on the reset arm. A iixed path is established for latch roll 32 by placing it on the end of reset arm 18 which rotates about a iiXe-d pivot point. The latch load is reduced to one-half by locating latch roll 32 twice as far from its pivot point as the action point of the biasing means comprising springs 24 and 24a is located. This helps to balance reset arm 18 about its pivot point and thus further contributes to stability. Reset arm 18 is adapted at its other end to be engaged by means, such as ram 36, which effect reset movement of the reset arm from its second position back to its first position. It is to be understood mechanism taken along that movement of ram 36 is related to movement of plunger 14 of pivot valve device 12. More specifically, with reference to FIG. 1, upward movement of plunger 14 caused by counterclockwise rotation of reset arm 18 is followed very quickly by upward movement of ram 36 which causes clockwise movement and `resetting of the reset arm.

The latch 22 of latch mechanism 10 is movably or pivotably mounted on a latch pivot pin 40 which is supported on support 16. Latch 22 has a first or latching position (shown) wherein it maintains reset arm 18 latched and is movable counterclockwise to a second or unlatching position out of its first position to effect release or unlatching of the reset arm. When latch 22 is in its first position, it is biased in a clockwise direction against a stop member 42 mounted on support 16 by means of a latch reset spring 44. Stop member 42 is a simple pin 42a covered with a small cylinder of resilient material 42b so as to minimize the transmission of shock through it to the latch.

Latch 22 is arranged so that it is perfectly balanced about its center of rotation. During the final grinding operation during its manufacture, the latch is revolved about its center of rotation while both the latch face 46 and the latch tail surface 48 are ground into perfectly cylindrical surfaces centered on the point of rotation. Thus, since it is symmetrical, neither translational nor rotational shock disturb its equilibrium. Latch 22 is provided with a pin 50 which projects from tail surface 48.

Means such as a solenoid 52 are provided to effect automatic counterclockwise pivotal or unlatching movement of latch 22 from its first position toward its second position. Solenoid 52 comprises a U-shaped yoke 54 which is rigidly mounted on support 16 by a bolt 56. Yoke 54 is provided with a solenoid coil 58 and a solenoid armature 60 is disposed therein, Yoke 54 supports an armature guard 62 against which the rear end of solenoid armature 60 is normally biased by an armature reset spring 64. When solenoid coil 52 is energized, armature 60 moves to the left (with respect of FIG. l) and strikes the upper end of latch 22 causing the latter to move counterclockwise (with respect to FIG. l) and thereby effecting unlatching of reset arm 18. Armature 60 is then returned to its normal position by spring y64. Solenoid 52, which is a relatively heavy mass, is mounted in such a manner with respect to the planes of principal shock and vibration that the resultant movement of its armature 60 in response to shock is minimized and is in a direction which will not result in its impinging against latch 22 accidentally,

Means such as a manual -operating device 68 is provided to effect manual counterclockwise pivotal or unlatching movement of latch 22 from its first position toward its second position. Manual operating device 68 is an alternative means of tripping latch 22 and is used instead of solenoid 52. However, manual operating device 68 must be mechanically trip free to provide for proper operation of latch mechanism and to prevent the hand of an operator from being injured if, after once manually tripping latch 22, the latch resets and is retripped automatically by solenoid 52 while the hand of the operator is still on or near the manual operating device.

Manual operating device 68 comprises a manual lever 70 which is pivotally mounted on a pin 72 carried by aV bracket 74 on support 16. Lever 70 is made from an elongated piece of thin resilient metal such as spring steel having front and rear edges 79 and 81, respectively, bent to Ushape.\lTo keep the edges of lever 70 from cutting the hand of an operator, the lever is covered at its outer or U-shaped end by a piece of heat shrinkable plastic tubing 76. Lever 70 is maintained in its normal or first position Within a stop or notch 77 in bracket 74 and biasing means such as a reset spring 78 bias it to first position. Lever 70 is manually pivotable in a clockwise direction (with respect to FG. 2) and is adapted so that front edge 79 of its lower end strikes pin 56 on latch 22 to cause the latter to move counterclockwise (with respect to FIG. l, as hereinbefore described). As FIGS. 1 and 2 show, the lower end of lever 70 has an outwardly bent tab 80 at rear edge 81 thereof which forms an inclined plane which rides on pin 50 of latch 22 to enable the resilient lever to be readily deflected out of the way by counterclockwise rotation (with respect to FIG. l) of latch 22 as pin 50 thereon strikes the inclined plane. AS will be understood, front edge 79 of lever 70 is adapted to engage pin 50 on latch 22 to cause movement of the latch. Rear edge 81 of lever 70 is adapted by the inclined planar surface of tab 80 so that any relative closing movement between the rear edge and pin 50 of the latch which results in engagement of the inclined planar surface of tab 80 and pin 50 causes deflection of the lower end of lever 70 away from pin 50. Tab 80 on lever 70 can be formed by providing a slot 85 therein which proceeds inwardly from rear edge 81 and by bending the portion of the strips between the slot and the end of the lever. Thus. the inherent resilient quality of lever 70 is utilized, not only to maintain the lever in notch 77 of bracket 74, but also to aid in the mechanically trip free operation of the lever.

The mass of manual operating device 68 is a small fraction of the mass of prior art manual operating devices and its arrangement on support 16 is such that it contributes little to the total mass supported on the support thereby reducing the effects of oscillation and vibration.

As will be understood, reset arm 18 and latch 22 rotate in the same first plane. Preferably, the first plane is generally vertically disposed so that the reset arm and latch balance about their-pivot points. Furthermore, resilient stop 42 is located in the first plane and solenoid armature 6i) also moves in the first plane. This a-dds to the stability and vibration resistance of the device.

Lever 70 rotates in a second plane which is transversely disposed with respect to the first plane. However, it could be otherwise disposed.

The invention operates as follows. Assume, first, that all components are in the position shown in the drawing, i.e., that latch mechanism 10 is in latched condition. Assume further that it is desired to trip latch mechanism 10 so that pilot valve device 12 ycan perform a useful function. It is to be understood that tall references to direction of movement of components hereinafter made are with respect to FIG. 1, except as otherwise noted. Solenoid 52 is energized to -cause its armature 60 to move to the left and strike latch 22 causing the latter to rotate counterclockwise.'The face 46 of latch 22 rolls off of latch roll 32 and reset arm is then able to move counterclockwise in response to the ibiasing action of springs 24 and 24a. As reset arm 18 pivots counterclock-wise, it lmoves plunger 14 of pilot valve device 12 rupward thereby causing the pilot valve device to perform its function. As aresult of operation of pilot valve device 12, ram 36 lmoves upward `and causes reset arm to pivot clockwise against the bias of springs 24 and 24a. Plunger 14 of pilot valve device 12 is returned to the position shown in FIG. l by its biasing spring 15.

As reset arm 18 is pivoting in the clockwise direction, latch roll 32 rolls down the side of latch 22 and the biasing action of spring 44 `causes clockwise pivoting of latch 22 which results in reengagement of latch roll 32 with latch face 46 of 'latch 22. As will be understood, spring 64 in solenoid 52 returns armature 60 to the position shown in lFIG. l las soon as the solenoid is deenergized.

In addition to being able to trip latch mechanism 10 by means of energizing or operation of solenoid 52, the trip mechanism can also be tripped manually to accomplish manual tripping. A hu-man operator grasps manual operating lever 70 at the plastic covered end 76 and moves it slightly upward (with respect to FIG. 4) to disengage it from notch 77. The lever 70 is moved clockwise (with respect to FIG. 2) to cause its lower leading edge 79 to strike pin 5t) on latch 22. This causes disengagement of latch 22 from latch roll 32 of reset arm 18 with the same results as hereinbefore described. As lever 70 continues to move clockwise it swings clear of pin 50 thereby allowing latch 22 to be returned to its first position shown in FIG. l. When the human operator releases lever 70, it is biased counterclockwise (with respect to FIG. 2) by its reset spring 78. Although pin 50 on latch 22 is now in the return path of the lower end of lever 70, lever 70 is able to move there past because the outwardly bent inclined tab 80 of lever 70 rides up on the end of pin 50 and the lever is deflected aside and is able to return to its first position.

In some instances after manual tripping, the human operators hand is still on the trip lever 70 while the lever is still out of its first position. Under this circumstance, if latch 22 which has reset should be retripped automatically in response to operation of solenoid 52, lever 70 permits pin 50 of latch 22 to move past the lever without transmitting rotational force to lever 70 which could injure the human operator. .in 50 on latch 22 is able to move past the lower end of lever 70 in the same manner as hereinbefore described, i.e., by engaging inclined tab portion 80 of lever 70 and causing sideways defiection of the lower end of lever 70 instead of causing rotational movement of the lever.

The embodiments of the sive property or lows:

1. In a latch mechanism,

a support,

a reset arm on said support and pivotable about a first point and having a first position and a second position,

said reset arm adapted to be returned to first position immediately after reaching second position,

a latch roll at one end of said reset arm,

means on said support for biasing said reset arm toward second position,

said means acting upon said reset arm between said first pivot point and said latch roll,

a movable latch on said support having a first position and a second position,

means for biasing said latch toward first position wherein one end of said latch engages said latch roll invention in which an excluprivilege is claimed are defined as folon said reset arm to maintain the latter in its first position,

electroresponsive means on said support for moving said llatch out of its first position,

and a movable manual operating lever on said support having a first position and movable out of said first position to engage the other end of said latch to move said latch out of its first position,

said lever having a resilient portion for engaging said latch which is adapted to bend out of the path of movement of said latch as the latter moves out of its first position in response to operation of said electroresponsive means while said lever is out of its first position.

2. A latch mechanism according to claim 1 wherein said latch is pivotable about and balanced about a second pivot point.

3. A latch mechanism according to claim 2 including a resilient stop means on said support for locating said latch in its first position.

4. A latch mechanism according to claim 3 wherein said electroresponsive means comprise a solenoid having a movable armature for moving said latch out of its first position.

5. A latch mechanism according to claim 4 wherein said reset arm and said latch rotate in a first plane, wherein said resilient stop means are located in said first plane, and wherein said solenoid armature moves in said first plane.

6. A latch mechanism according to claim 5 wherein said lever rotates in a second plane which is transverse to said first plane.

7. A latch mechanism according to claim 6 wherein said first plane is substantially vertical.

References Cited UNITED STATES PATENTS 3,038,047 6/1962 Marquis 200-116 3,185,793 5/ 1965 Ellenberger 200-116 3,213,243 10/1965 Anderson et al 200-122 3,214,537 10/1965 Krieger 335-22 BERNARD A. GILHEANY, Primary Examiner. H. BROOME, Assistant Examiner. 

